Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4'-(1H-1,2,4-triazole-3,5-diyl)dibenzoate

The asymmetric unit of the title compound, catena-poly[[[aquabis(pyridine-kappa N) cadmium(II)]-mu(2)-4,4'-( 1H-1,2,4-triazole- 3,5-diyl)dibenzoato-kappa(4) O,O': O'',O'''] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)(2)(H2O)]center dot 4.5H(2)O} n or {[Cd(bct)(py) (2)(H2O)]center dot 4.5H(2)O} n (I), consists of a Cd2+ cation coordinated to one bct(2-)carboxylate dianion, two molecules of pyridine and a water molecule as well as four and a half water molecules of crystallization. The metal ion in I possesses a pentagonal-bipyramidal environment with the four O atoms of the two bidentately coordinated carboxylate groups and the N atom of a pyridine molecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water molecule occupy the axial positions. The bct(2-) bridging ligand connects two metal ions via its carboxylic groups, resulting in the formation of a parallel linear polymeric chain running along the [111] direction. The coordinated water molecule of one chain forms a strong O-H center dot center dot center dot O hydrogen bond with the carboxylate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) angstrom between the cadmium ions belonging to different chains. Aromatic pi-pi stacking interactions between the benzene fragments of the anions as well as between the coordinated pyridine molecules belonging to different chains results in the formation of sheets oriented parallel to the (101) plane. As a result of hydrogen-bonding interactions involving the water molecules of crystallization, the sheets are joined together in a three-dimensional network.